In a conventional method of making ice by circulating ice-making water to the ice making member having a refrigerating system, a period of time of an ice making operation has been controlled by a timer. According to such a conventional method, when a period of time preset to the timer has been long, ice having a relatively large thickness has been made, and when such preset time has been short, ice having a relatively smaller thickness has been made. However, even if a period of time preset to the timer has been suitable, the thickness of ice made has varied with the ambient temperature. It has therefore been impossible to make ice having a predetermined thickness.